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Audio Modes

Perfect Speech Intelligibility

Overview

Intercom Stations support three audio modes

  • OpenDuplex® operation: maintains open communication lines in both directions to allow for natural, fully hands-free conversations.
  • Switched Duplex operation: detects and switches the communication direction automatically.
  • Simplex operation (PTT = Push to Talk): allows for manual control of the communication direction; a button must be pressed before speaking.
Commend’s OpenDuplex® technology includes a powerful echo cancellation algorithm to improve speech quality, even in 16 kHz eHD Voice audio quality.

Actual distance: 3,935 km // Felt distance: 1 m

22:47

Incoming call from a car park in Perth. A customer is having difficulties paying with her credit card at the exit gate.

22:48

The call centre agent responds to the request by talking the customer through the payment process, then wishes her a nice evening.

A natural communication experience as loud and crystal clear as a face-to-face conversation...

...made possible by a Commend Intercom system.

  • OpenDuplex
    OpenDuplex Schematic

    OpenDuplex®

    This type of speech control allows simultaneous talking and listening and provides top quality speech intelligibility.
    • The conversation is permanently switched through in both directions, therefore both conversation partners can speak simultaneously.
    • The OpenDuplex® mode allows an improvement in speech quality at high ambient noise levels.
    • OpenDuplex® is carried out by Echo Cancelling in the station.
    • Should not be confused with Full-Duplex which is similar but without echo cancelling and therefore only works correctly when one side is using a gooseneck microphone or headset.

  • Switched Duplex
    Switched Duplex Schematic Drawing

    Switched Duplex

    With this type of speech control, a duplex controller controls the direction of speech. Only one person can speak at a time.
    • Speech communication in both directions, in which the louder sound source (usually the speaking person) determines the direction of the speech connection. This means the loudest side speaks and the other listens.
    • Perfect intelligibility up to a distance of 7 meters from the station, without pressing a button – the distance depends on the ambient noise.
    • The speech direction is determined by the “speech balance” (duplex controller).

  • Simplex
    Simplex Schematic Drawing

    Simplex

    This is the earliest type of speech control where the speech direction is controlled 
    manually. Only one person can speak at a time.
    • Speech communication only in one direction that is controlled by pressing the talk button. Also known as press-to-talk, release to listen.
    • Simplex is used for manual speech control, e.g. areas with high ambient noise.
    • Possible configuration:
      • Conversations fixed Simplex (the speech direction after initiating a conversation can be defined).
      • Simplex by pressing a button (the button must be held down to talk and released to listen).
      • Simplex by momentarily pressing a button. The other person must press the button to reverse speech direction.
Speech Intelligibility